Investigation of a parallel contact force robotic end-effector for thin-walled parts grinding and deburring with uncertain position

• Published in: Precision engineering Vol. 96; pp. 587 - 599
• Main Authors: Xu, Du, Mo, Haijie, Zhong, Zhiguo, Yin, Lairong
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.10.2025
• Subjects: Constant-force mechanism; Hybrid stiffness; Passive compliance; Precision machining; Robotic deburring; Thin-wall manufacturing; Precision machining; Hybrid stiffness; Constant-force mechanism; Passive compliance; Robotic deburring; Thin-wall manufacturing
• ISSN: 0141-6359
• DOI: 10.1016/j.precisioneng.2025.06.021

This paper focuses on the force overshoot problem that occurs in the initial contact phase of a robotic end-effector, a novel passive compliant constant-force end-effector designed to address the challenge of contact force stabilization and response in robotic grinding and deburring of thin-walled parts. Unlike conventional active force control methods that suffer from force overshoot due to dynamic response limitations, the proposed solution integrates a hybrid stiffness mechanism combining positive (multi-layer bending structures) and negative (inclined beams) stiffness elements to achieve sensor-less force regulation. The design features a parallel architecture with 120° distributed limbs, ensuring coaxial force distribution and vibration suppression. A comprehensive analytical model is developed, incorporating combined stiffness theory and elliptic integrals to characterize the negative stiffness beam's buckling behavior, with parameter optimization to maximize the constant-force stroke. Finite element analysis confirms uniform stress distribution under multi-axis loading (100N force/20N·m torque), while experimental validation on magnesium-aluminum alloy workpieces demonstrates the mechanism's ability to maintain contact force within ±5 % deviation over a 4.5 mm stroke range, even with ±2 mm positional errors. The passive design eliminates the need for complex control systems, offering significant advantages in cost reduction, process adaptability through quick-change couplings, and scalability for diverse thin-wall geometries. This paper provides an insight into the potential of purely passive methods in achieving accurate and smooth force control. •An integrated passive compliant end-effector with positive and negative stiffness was proposed to achieve sensorless constant force regulation through a parallel architecture.•A comprehensive stiffness model is developed by combining elliptical integration and parameter optimization to analyze the buckling behavior of negative stiffness beams and maximize constant force range.•Smooth force control experiments were conducted for deburring and polishing tasks on Aluminium alloy thin-walled components, with contact force deviation stabilised within ±5%.